Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.46	4.741%	$151.3088	$151.31	$151.30	$151.30
Purchase #2	$229.36	10.566%	$253.5942	$253.59	$253.60	$253.60
Purchase #3	$204.85	11.717%	$228.8523	$228.85	$228.85	$228.90
Purchase #4	$181.52	3.743%	$188.3143	$188.31	$188.30	$188.30
Purchase #5	$114.38	9.742%	$125.5229	$125.52	$125.50	$125.50
Purchase #6	$59.49	6.476%	$63.3426	$63.34	$63.35	$63.30
Purchase #7	$49.83	9.824%	$54.7253	$54.73	$54.75	$54.70
7 purchase totals =	$983.89		$1,065.6604	$1,065.65	$1,065.65	$1,065.60